The house-fly, Musca domestica Linn: its structure, habits, development, relation to disease and control . Each of the large marginal sensorybristles {) of the aboral surface has a fine channel running downthe whole length of the seta. This channel communicates withthe cavity of a pyriform mass of nerve-end cells {), consisting offive or six cells. These masses of cells occupy a large part of theinterior of the oral lobes. As these gustatory bristles are exposedand directed ventrally when the proboscis is retracted, they mayassist the fly in testing the nature of its food before extend
The house-fly, Musca domestica Linn: its structure, habits, development, relation to disease and control . Each of the large marginal sensorybristles {) of the aboral surface has a fine channel running downthe whole length of the seta. This channel communicates withthe cavity of a pyriform mass of nerve-end cells {), consisting offive or six cells. These masses of cells occupy a large part of theinterior of the oral lobes. As these gustatory bristles are exposedand directed ventrally when the proboscis is retracted, they mayassist the fly in testing the nature of its food before extending itsproboscis. On the oral side of the oral lobes the nipple-like 62 INTERNAL STRUCTURE OF HEAD AND PROBOSCIS gustatory papillae (figs. 3, 30, ) have already been aperture at the end of the papilla leads into a fine duct, whichends in a pyriform sensory bulb (). The tracheae (tr.) canbe seen running through the cells, some of which contain severalnuclei, and from their appearance are probably derived from thefat-body. No tracheal sacs could be found either in the oral lobes. ^s--f-- FiG. 30. Portion of a transverse section of the oral lobes, showing the two types ofgustatoij sense organ, etc. Gustatory seta. g.}}. Gustatory papilla. hy. Hypodermis under which lies a pigmented layer. Pseudo-trachea in section. Sensory bulb of gustatoiy papilla. .s.^j. Sensoij bulb of gustatoiy seta. tr. Trachea. or at their bases, but the annular tracheae are continuous withthose of the proboscis. The haemocoel of the oral lobes is welldeveloped. This supports the view set forth by Kraepelin, andwith which I agi-ee, that the inflation of the oral lobes is due to theblood. I consider that the extension of the proboscis is due to theinflation of the tracheal sacs of the head. The proboscis having LABIAL SALIVARY GLANDS 63 been protruded the oral lobes are then diverged by the contractionof the retractor muscles of the furca and discal sclerites, and dis-tende
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishercambridgeuniversit
